The Gulf Stream is typically 100 kilometres (62 mi) wide and 800 metres (2,600 ft) to 1,200 metres (3,900 ft) deep. The current velocity is fastest near the surface, with the maximum speed typically about 2.5 metres per second (9 kph; 5.6 mph).

History

European discovery of the Gulf Stream dates to the 1512 expedition of Juan Ponce de León, after which it became widely used by Spanish ships sailing from the Caribbean to Spain.[1] A summary of Ponce de León's voyage log, on April 22, 1513, noted, "A current such that, although they had great wind, they could not proceed forward, but backward and it seems that they were proceeding well; at the end it was known that the current was more powerful than the wind."[2] Its existence was also known to Peter Martyr d'Anghiera.

Benjamin Franklin became interested in the North Atlantic Ocean circulation patterns. In 1768, while in England, Franklin heard a curious complaint from the Colonial Board of Customs: Why did it take British packets several weeks longer to reach New York from England than it took an average American merchant ship to reach Newport, Rhode Island, despite the merchant ships leaving from London and having to sail down the River Thames and then the length of the English Channel before they sailed across the Atlantic, while the packets left from Falmouth in Cornwall?[3]

Franklin asked Timothy Folger, his cousin twice removed (Nantucket Historical Society), a Nantucket Island whaling captain, for an answer. Folger explained that merchant ships routinely crossed the then-unnamed Gulf Stream—identifying it by whale behavior, measurement of the water's temperature, and changes in the water's color—while the mail packet captains ran against it.[3] Franklin had Folger sketch the path of the Gulf Stream on an old chart of the Atlantic and add written notes on how to avoid the Stream when sailing from England to America. Franklin then forwarded the chart to Anthony Todd, secretary of the British Post Office.[3] Franklin's Gulf Stream chart was printed in 1769 in London, but it was mostly ignored by British sea captains.[4] A copy of the chart was printed in Paris circa 1770–1773, and a third version was published by Franklin in Philadelphia in 1786.[5][6] The inset in the upper left part of the 1786 chart is an illustration of the migration pattern of herring and not an ocean current.